Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$6.55	12.108%	$7.3431	$7.34	$7.35	$7.30
Purchase #2	$13.42	3.866%	$13.9388	$13.94	$13.95	$13.90
Purchase #3	$65.88	9.148%	$71.9067	$71.91	$71.90	$71.90
Purchase #4	$29.49	11.738%	$32.9515	$32.95	$32.95	$33.00
Purchase #5	$222.34	12.389%	$249.8857	$249.89	$249.90	$249.90
Purchase #6	$28.40	3.687%	$29.4471	$29.45	$29.45	$29.40
Purchase #7	$108.98	9.790%	$119.6491	$119.65	$119.65	$119.60
7 purchase totals =	$475.06		$525.1220	$525.13	$525.15	$525.00